Process of and apparatus for converting high-boiling oils or hydrocarbons into stable low-boiling oils or hydrocarbons



Dec. 21 1926. 1,611,615

PROCESS OF AND APPARATUS FOR CONVERTING HIGH BOILING OILS OR D. L. THOMAS HYDROCARBONS INTO STABLE LOW BOILING OILS OR HYDROCARBONS Original Filed April 24, 1919 3 Sheets-Sheet 1 4 WATTORNE Dec. 21 1926. 1,611,615

D. L. THOMAS PROCESS OF AND APPARATUS FOR CONVERTING HlGH BOILING OILS 0R HYDROCARBONS INTO STABLE LOW BOILING OILS OR HYDROCARBONS Original Filed April 24, 1919 3 Sheets-Sheet i BY W 3 4} ATTORNEY.

Q TOR.

Dec. 21 1926.

D. L. THOMAS v PROCESS OF AND APPARATUS FOR CONVERTING HIGH BOILING OILS OR HYDROCARBONS INTO STABLE LOW BOILING OILS OR HYDROCARBONS 3 Sheets-Sheet 5 Original Filed April 24,1319

# ATTO NEYS.

Patented Dec. 21, 1926.

UNITED STATES PATENT OFFICE.

DONALD LEE THOMAS, OF NEW YORK, N. Y.

PROCESS OF AND- APPARATUS FOR CONVERTING HIGH-BOILING OILS OR HYDRO- CARBONS INTO STABLE LOW-BOILING OILS 0R HYDROCARBONS.

I Application filed April 24, 1919, Serial No. 292,425. Renewed May 15. 1926.

This invention relates to a method and uized standard methods of cracking oils bv apparatus for the conversion of high-boil-\n1eans of heat and pressure, each capable of ing oils, for example petroleum residual oils of the parafiin series, or other suitable hydrocarbons into stabilized products having a much lower boiling point.

This is preferably accomplished in two- 'stages, by first cracking the hydrocarbons by heat in the manner herein described and then preferably condensing the products of the reaction Whilst under pressure, although prior to such condensation the products may be further treated in any desired manner.

The amount of heat required is that which is necessary to furnish the expansive force needed to bring about rupture of the original hydrocarbon molecule, whilst pressure isnecessary to force together the resulting nascent reactive products into more concentrated and intimate relationship so that re actions involving new molecular arrangements can thereafter take place in a second and preferably separate stage of the process.

As all cracking operations require more or less mechanical force for their development, it is customary to obtain this force from the expansive power of the oil-vapours developed under pressure. The pressure in this last mentioned case, when present during the decomposing stage of the process, naturally opposes the expansive force needed to bring about rupture of the hydrocarbon molecules, hence, at this point it is a detriment, whilst during recombination, as it favors reunion of the cracked products, it is a sine-qua-non of operation.

From these facts 'I have ascertained that the cracking operation should take place in the following series of steps 1st.-A vaporization of the oil, under pressure, at moderate temperatures, for example at from 400 to 500 0., to develop suificient Working force to operate the apparatus.

2nd.Cracki ng of the oil-vapour at higher temperature, for example at from 500 to 800 0., under low pressure to produce chemical dissociation.

3rcl.-A condensation of the cracked products, under high pressure in order to favor molecular recombination.

At present there are at least three recogillustration by a type. First, the so-called, Burton-process, consisting of heating a large body of liquid oil in a large tank or .still, and condensing the vapours generated there- 1n, under pressure. Second, the so-called Rittman-proce'ss, consisting of heating oilvapors under pressure, in a large (12 inch) tube and then condensing the cracked products so produced, under pressure.

Third, the socalled Hall-process, which consists of heating the .oil in a long coil of small bore pipe, (1 inch diameter and 600 feet long) releasing the pressure so produced, by expanding the vapours down to atmospheric pressure in a large tank or chamber and then again recompressing the gases and vapours by means of a mechanical compressor, in order to polymerize them, and then finally condensing the resulting products to liquids, under pressure.

To these may be added a fourth type, as exemplified in my process illustrated herein, wherein the selected oil is first vapourized under pressure and the vapour so generated, passed into a region of low pressure. High temperature is then applied to the vapours in this region of low pressure in order to crack the same, and the cracked products are then passed to a region of high pressure for recombination and polymerization.

To carry out the process outlined above, recourse is'had to an apparatus termed a Venturi tube. Such apparatus, as is well known, consists of a combination of conical converging and diverging nozzles connected at their smaller ends by a throat piece of greater or less length. An apparatus of this character has the notable property of converting, potential or pressure energy, directly into kinetic or velocity energy, with a corresponding resulting diminution of pressure at the point of highest velocity, and furthermore reconverting this kinetic energy back once moreinto potential or pressure energy, with very little pressure loss.

The advantages of an apparatus of this nature, for producing variation of pressure and velocity, over any possible equivalent arrangement of mechanical compressors is at once apparent.

It is to be understood, that, under this term of Venturi tube I here intend to include not only a duct composed of two str.ctly conical frusta having their small ends contiguous or adjacent, such as forms part of the well known Venturi meter itself, but any duct the cross-section of which diminishes in any other manner to a minimum and then increases, so long as it-is adapted to fulfill an equivalent function as regards the interconversion of velocity and pressure without substantial losses due to eddy-making, distortion, or obstruction of the stream lines and the like causes.

A specific example of-a one-tube installation is fully set forth and described in the following s ecification and drawings forming a part hereof, in which- Figure 1, is an elevation, partially in section of a form of the apparatus, embodying my invention.

Figure 2, is also an elevation partially 1n section, of a form of an apparatus embodying my invention essentially similar to Fig. 1, but somewhat enlarged, in order to show the subsidiary devices thereof and the location of certain of said parts being somewhat rearranged with respect to Fig. 1, though functioning essentially the same.

Figure 3, is a longitudinal detail vertical section showing the structural form of the Venturi throat piece, and its containing chamber.

Figure 4, is a transverse vertical section on the line 4 4 of Figure 3, of the Venturi throat piece and its chamber.

Figure 5, is an enlarged (full size) detail longitudinal vertical section of one of the steps on the Venturi throat piece, with one of the holes or passages that are bored there- 1n.

Figure 6. is a detail vertical section of one form of 'flange and joint connection for fastening the removable door to the casing which carries'the Venturi throat piece shown in Figures 3 and 4.

Figure 7 is a detail vertical section of a modified form of flange and joint connection for the said removable door.

Figure 8, is a vertical section and Figure 9, a cross section of one of the short pieces of ll'OIl pipe used as filling material for the digester.

Referring to Figure 1, the Venturi tube therein shown is constituted of an upper converging mouthpiece or chamber, 1. which may be for example 12 inches internal diameter at its upper and widest section, and 3 inches internal diameter at .its lower and narrowest section, although I do not confine nor restrict myself to these dimensions.

Externally this converging mouthpiece is heated by a as-fired furnace, 2, of the surface combustion type, deriving its fuel supply from the gas-main hereinafter described, fuel being supplied under any desired pressure, say about one atmosphere.

This converging mouthpiece serves merely as the vaporizing chamber for'the'oil, and is in no way intended to crack the hydrocarbon which is suppl'ed to it in the form of a tine spray from the centrifugal sprayer, 3, connected with the oil-feed pipe (it) and fed with oil under high pressure by the pump, 4. This oil before admission to the vaporizing chamber should have its temperature raised to the "olatilizing point, by a separate external oil-heater 4. In this way the vaporizing chamber ,is only called upon to supply the latent heat of vaporization of the oil. This is a very important point, as the heating surface is limited, and without preheating, very high furnace temperatures might be necessary in order to secure adequate vaporization.

In order to insure an absolutely constant and uniform flow of 'oil at all times such for example as with a standard grade of fuel oil of 0.850 spec. grav-., a constant-flow-valve, 5, is fitted in the oil-line.

An oil-meter, 6, is located in the oil-line in order to record the rate of oil-feed.

The length of the conver ing portion of the Venturi tube from the flange, 1, t0 the flange, 1", may be 8 feet.

The tube is surmounted by a cylindrical extension or cap, 7, of some, 12 inches. internal diameter and some 2 feet in height preferably, although I do not confine nor restrict myself to the dimensions already or hereinafter set forth.

The lower diverging Venturi mounthpiece, 8, acts as the retarding section of the tube for reconverting the velocitv or kinetic energy of the vapours back into pressure. The diameter internally is 12 inches at the lower and widest section decreasing to 4 inches at the upper and narrowest section. The length from the flange, 8, to the flange, 8", is 10 feet.

The construction is practically similar to that of the converging mouthpiece, differing therefrom merely in having attached to its lower end the down-take, 9 (see Figure 2),

enclosed in a tubular steel casin or base, 10. This down-take, 9, serves to deliver unvaporized Oll, asphalt residium, carbon, and

tar, formed during the cracking operation into the sludge-box 11, from which it is continuously and automatically removed by the valve, 12, the liquid level being maintained by said valve about on the line, 1313, slightly below the mouth of the down-take, 9, which is left open to afford free escape of the gases and vapours into the space, 13.

From the space, 13, a ipe, 14, leads the cracked products to the igester, 15. This consists of a stout steel chamber 24 inches internal diameter and 12 feet high, tilled with short pieces of 1 inch iron pipe such as illustrated in Figures b and J. g

It is to be understood that the object of the digester is to treat the hydrocarbon material by exposing it to large surfaces by which it is naturally adsorbed, whilst the speed of travel of the vapours is reduced to a minimum. Such surfaces exert a catalytic or some similar effect on the cracked material which is in a highly reactive condition, bringing about hydrogenation, polymerization and recombination of the nascent fragments of the original hydrocarbon molecules into new molecular arrangements. This-action is of course assisted by pressure, because, according to the law of mass action, reaction velocity is proportional to concentration and concentration is directly proportional to-pressure. Surface action has a great deal to do with the effects produced as is pointed outby Professor \Vilber D.

Bancroft in a Note on contact catalysis- Journal of Physical Chemistry, June, 1918, page 433, wherein it is shown that the equilibrium and velocity relations of physical substances is markedly altered by adsorption, much freer play being given to physical and chemical forces thereby. \Vhatever the cause may be, the action is unquestionable, being more cumulative than instantaneous and it takes place whether the hydrocarbon is in liquid or gaseous state when brought into contact with the battling material.

It appears that two entirely difl'erent reactions are involved in the formation of light hydrocarbons. The first one involves splitting of saturated bodies into saturated and unsaturated, paraflins and olefines of lower molecular weight resulting, with the splitting out of hydrogen, and consequent mcrease in volume of cracked products. Diminished pressure facilitates and accelerates this stage. The, next step however, requires the condensation and hydrogenation of the unsaturated bodies, and pressure naturally favors this. It is true that hydrogen may split out also at this point, but even so, con

densation and hydrogenation is difficult to effect under diminished pressure, therefore suiiicient pressure must be provided to effect this condensation since the natural tendency of pressure is to force homogeneous gas reactions in the direction in which a reduction in the number of molecules takes place, accompanied by synthesis in the reactive material.

Referring again to Figure 1 the external walls of both the diverging Venturi mouthpiece, 8, and of the tubular base, 10, as well as the digester, are to be enclosed in heat retaining jacket, 15, of asbestos or other suitable material.

The throat piece, 16 (see Figures 2 and 3), of the Venturi tube is formed with conical shaped, downwardly inclined holes, 17, in its walls, leading from the exterior surface into the interior of the throat. These holes, 17, are bored'in steps, 18, which are formed on the outer surface of the Venturi throat piece, as is bestsecu in Figure 3. Their exact diametcr is preferably inch at the point, 18, on the outer surface, and inch at the point, 18", on the inner surface, see Figure 5. There are 15 of these holes in each step, and there are 16 steps formed on the throat piece, making the total number of holes equal to 240. As the inner diameter of each hole is inch, its area equals .1963?) square inch, and the total area of the 240 holes is therefore 47.124 square inches. In order that there shall be no escape of oilvapours through these holes it is necessary that the pressure in the space, 19, surrounding the throat piece, shall at all times exceed that in the throat interior. This is provided for by having the area of the gas supply pipe, 20, greater than the total combined area of all the holes in the walls of the throat piece. By making the area of the pipe, 20, greater than the total area of the 240 holes (47.124 square inches) this result is a complished. Thus a pipe 8 inches in diameter or larger will give this result. It may be stated here, that the throat piece is formed from a cast steel tube with walls originally 1 inches thick, into which the steps 18 are turned by means of a lathe in such manner as to permit the central axis, 1818, of the holes, 17, (Figure 5) to make an angle of 45 degrees with the central axis of the throat piece, (Figure 3). The whole construction is very similar to that of the throat piece of the well known Schutte ejector condenser.

The casing, 21, is formed of rolled steel 1 inch thick, bent to the shape shown in Figure 4. The ends 22 and 23 of the casing as well as the flange, 24, are cut out separately to-proper size and shape and the different parts are then welded together to form the complete casing.

The throat piece itself is made removable from the casing, 21, by means of a door, 25, which closes the casing by being bolted to the flange, 24, on the casing. This arrangement is for cleaning purposes in case carbon deposits should form on the throat piece. In order to hold the throat piece in position and at the same time connect it with the Venturi tube, two tubular connections, 26. and 27 are provided. The connection, 26, as well as the end of the throat piece is at this point cut off at such an angle as to permit of easy removal turning in the socket by means of a tongue and groove, 28, the tongue being formed on the piece, 27, and the groove cut on the end of the throat piece at the point where it enters the socket.- This at all times msu res perfect alignment of all the parts wlnlst quick and easy removal is permitted.

The pieces, 26, and, 27, are firmly held in place against movement and rotation, when the converging and diverging sections of the venturi are bolted to the casing, 21.

In order to support the'upper connection, 26, as well as the thoat piece itself, the cusing, 13, has bolted to its back-wall a semicircular sector supporting piece, 29, as clearly shown in Figures 3 and 4, whilst the complement to this, thesemicircular sector support ing piece, 30, is riveted to the removable door, 25. Inspection of the varlous figures will clearly show that as soon as this door is bolted in place, the Venturi throat piece is firml locked in position, whilst u on opening tlie door, it is readily removab e.

Figures 6 and 7 show flange connections for attaching the door, 25, to the casing, 21.

p Patent No. 376,829, and

Figure 6 is a standard type, consisting of flat ground surfaces fitted with a corrugated soft copper gasket, 31, between, to render it gas-tight. Figure 7 is a type of ground-joint, developed by F. Haber and t. Le Rossignol, in their synthetic ammonia process, see Z. Elektrochem, 1913 vol. '19 53-72-orGerman it consists of two beveled surfaces 32, and, 33, of differing an gularity, ground so as to form at the -po1nt of junction, a line contact surface only, the angular surface of the cover has a more acute angle (16 degrees) than the angular portion of the bore or casing (20 degrees) powerful bolts fitting through 'the flanges serve to draw the surfaces firmly into effective contact, forming a perfect gas-tight joint capable of standing up indefinitel under ex tremely high temperatures an pressures. This type of joint is to be preferred, for all points of the apparatus, no matter of what shape, which are called upon to resist high temperature and high pressure, and its extenslve use throughout the, plant will obviate many of the structural difiiculties encountered in this type of apparatus.

Referring again to Figure 2, it will be seen that a pipe, 20, finds entrance to the space 19, in the casing, 21. This pipe is for introducing into the casing, superheated gases or vapours, preferably derived from the process itself, for the urpose of cracking the oil-vapours in the enturi throat by admixture therewith. The gases used for this purpose may eitherbe introduced into the system from an external source, by means otthe pipe, 34, and valve, 35, or, they are preferably, as stated above, the non-condensable gases produced durin operation of the process and arebrought from the storage tank,36, by way of the pipe, 37.

A pipe connection, 38, has a gas-releasing pressure regulator, 39, at its upper end to permit any excess of gas to escape from the system to a fuel supply tank or gas-holder not shown in the drawin A connection, 40, leads a portion of the non-condensable gases to a superheating coil, 41, located in a recess in the wall of the gasfurnace, 2. B examining the drawing it will be seen, tiat the gas drawn from the pi e, 40, passes through a three-way-cock or va ve, 42. 1

This cock has a pipe, 43, forming a bypass connccting it with the pipe, 20. By

\ manually manipulating this cock or otherwise, variable quantities of cool gas from themain, 40, are sent through the superheater, 41, and the. by-pass, 43, to meet at the point, 44, thus permitting of varying the temperature of the mixture over a wide range, by varying the ratio ofc'admixture, before its introduction into the casing, 21, the valye, 45, controllable by hand or otherwise being used to vary the quantity but not the temperature of the gas-mixture so introduced.

A pressure gauge, 46, is connected by the pipe, 47, with the interior of the venturi near the throat, as shown also in Figure 3, this is inorder to show the immediate and true pressure therein at all times.

In cracking oils under pressure, it is usually found that many and various constituents are produced at one and the same time in the zone of reaction. Now for any one particular set of conditions as regards temperature and pressure, these constituents are always found to be produced in a definite fixed ratio to each other, although. all are formed at one and the same time. Now if, by any artificial means we continuously remove, or introduce from an external source, one or more of these said constituents into the sphere of the reaction, we alter as it were the equilibrium conditions of the system, which promptly responds by an effort to make good the loss where such exists, or to check the specific formation of the constituent or constituents present in excess, thus returning the system to a state of equilibrium.

The bearing that this statement has upon this process is due to the fact that we use the superheated gases derived from the process itself for heating and cracking a subsequent portion of the oil-vapours.

The effect of using such gases in this way is to check the formation of these gases, in the zone of reaction, from the hydrocarbon material being cracked, because .where any excess exists the tendency is, as pointed out above, for the system to cease producing the constituent present in excess, at least for the time being until equilibrium conditions are restored.

Stated in another way, the addition of.

' any of the end products, in any decomposition process, checks decomposition in that direction and causes it to proceed in another and more desired direction thus conserving valuable material. In this process the high concentration of the end-product gases in the reaction zone is sufficient to prevent further formation of these undesirable products and permits the possibility of making gasolene and other light products without evolving further amounts of gas" in other words it may be said that the evolved gas enters into chemical union as fast as it isformed, that is, a state of chemical equilibrium exists.

In the cracking of hydrocarbons by heat, the control of the operative conditions forms perhaps the most important element of the process, although little attention is usually paid to it by designers. The reaction, if reaction it can be called, is a very complex one, where slight variations of time, temperature, pressure, speed of oilfeed, and their various combinations, make wide divergence in the results; for these reasons, if for no others, some style of automatic control quickly responsive to changing conditions, is a solutely essential, because no human control no matter how well carried out can meet all the constantly varying conditions that confront the operator of an oil-cracking process.

For the above stated-reasons, this process is fitted with automatic means of temperature control as well as of oil-feed. The apparatus proposed for this purpose is not the delicate and intricate types employed for laboratory research wherein it is usually necessary to keep the conditions fixed within extremely narrow limits, but is of a much more robust type suitable for every day op-- erativc use. Usually if the temperatures of operation can be kept within five degrees cent, plus or minus some fixed point satisfactory results will be attained. The type of thermostat it is proposed to use for this purpose is of the gas or vapour-pressure type, consisting of a chamber containing a chemical substance capable of developing gas or vapour under pressure, when sub jectcd to the temperaturesthat'are to be controlled. The pressure so developed is used to operate, first,-an indicating instrument, similar to a pressure gauge, but calibrated for temperatures instead of for pressures, sccond,a mechanically responsive device in the nature of an oil-pressureoperated servo-motor, so designed as to adjust the various fuel and temperature controlling valves in such manner as to correct any variations from a fixed optimum temperature.

The type of thermostat best suited forthis purpose is one of a nature such as disclosed in U. S. Patent No. 1,159,893 which consists of a hermeticallysealed chamber, containing a solid chemical compound termed copper sulphate pentammoniate (CuSO,5NH,) WlllCll on being heated evolves large amounts of a1nmonia-gas (NH the pentammoniate degenerating into copper sulphate tetrammoniatc ousoaum On cooling, the ammonia is again absorbed and the original compound reformed.

The servo-motors employed with the above to operate the temperature control valves, are

very small affairs, not larger than a doorcheck and are operated b oil. under pressure from the pump 4, supplied to the valves of the servo motors by the pipe 70. The only part played by the thermostats is to operate the pilot-valves of these motors in conformity with the temperature changes taking located in the interior cover of the converging Venturi mouthpiece, above that level of the tube that is subject to direct furnace heat, but still being in direct contact with the .hot gases and vapours generated within the tube, thus the amount of gas pressure developed by the heat of these vapours, acting on the pentammoniate contained within the thermostatic chamber, is exactly proportional to their temperature, and the pressure of the gas so developed acting through pipe 49 is used to operate,first a temperature indicating device 49,second a pressure movable element 50 connected to the pilotvalve of the servo-motor, 50. This servomotor then operates an air and inert-gas mixture throttle valve, 51, which by means of air ports therein, and a pipe connection,

51., to the flue of the gas-furnace gives avariable air-inert-gas mixture corresponding to the desired temperature to be maintained' This mixture on being added to the fuel-gas gives a combustible mixture the flame temperature of Which'varies according to the ratio of inert-gas to air. The pipe, 52, carries the air and inert-gas mixture to the supply main 54 to which the burners, 53, are attached. As the fuel-gas in the main, 54, is usually under a pressure of 10 to 15 lbs. per square inch, the burners employed are ordinarily of the injector type so as to draw in air by suction. In actual practice two supply mains one above the other and both encircling the furnace are used, the upper one, 54, being used for the air and inert gas mixture, whilst the lower one, 54, is for the individual control overthe fuel-gas and airinert-gas supply to each burner. The variations of the ratio of air to inert-gas in conformit with the movements of the thermostat, course alters the ratio of flame temperature of all the burners equally, the

action being due to increasing or decreasing the rate and intensity of combustion of the fuel, this is of course in conformity with well understood princi les. time however the feed w ich controls the individual temperature of each burner is capable of manual adjustment by means of the aforesaid control valves which permit of altering the fuel and air supply to suit the conditions. This forms a very desirable arrangement, for whilst the working temperature of the furnace is automatically varied to suit conditions, yet any inequality in heating can readily be corrected by manual adjustment of the proper burners.

By the means just described a uniform temperature of the oil-vapours in the vaporizing chamberof the Venturi tube is main-- tained, with a consequent uniformity of vapour temperature. However where it is necessary to maintain the vapour pressure absolutely constant, recourse may be had to controlling the furnace temperature by means of the vapour-pressure itself as developed in the vapourizing chamber of the venturi. This can be done by dispensing with the pentammoniate container, 48, and admitting the oil-vapour under pressure directly to the movable member of the thermostatic element controlling the servomotor, 50 as shown in Fig. 2. In this way this motor is caused to adjust the throttle mixing valve in conformity with the actual ressure existing in the vapourizing chamber of the venturi, which of course effects the temperature changes of the furnace in a manner already described.

Cracking of the oil-vapours, in this process, is. brought about by admixture therewith of superheated gas in such quantity as to bring the temperature of the mixture ,up to the desired point usually 500 to 600 degrees cent. for gasolene, and 600 to 700 degrees cent. for aromatic hydrocarbons.

Now in order to compensate for any variation in the quantity or rate of flow of the oil-vapours or any variation in their temperature, two methods of control of the suerheating gases present themselves, one is y keeping their temperature constant and At the same rate of flow constant and varying the temperature of the gases. 4

The first method is to be preferred as it requires no variation in the actual heating of the gases which may be heated at some fixed temperature, provided it is high enough, the temperature variations being corrected merely by variation in the rate of flow. This permits of using a superheater located in the vapourizing furnace, asshown in the drawing, if desired.

In order that the temperature of the gases in the pipe, 20, shall be always uniform, the three-way valve, 42, is so arranged as to pass the same quantity of gas, no matter what its setting, this means that the total area of two of its openings shall be always the same, the only effect of varying its setting being to vary the ratio of gas passed through one opening to the superheater, 41, to that passed by theother opening directly through the by-pass, 43, the total quantity passing through both to the connection, 44, being always the same, the ratio of one to the other only being varied. In order to make the three-way-valve responsive to changes in temperature of the gas in pipe, 20, a thermostatic chamber, 55, containing pentanm'ioniate surrounds the pipe, 20, near its entrance into the casing, 21. A pipe, 56. leads the gas under pressure from this chamher, first to a temperature indicator, 57, and thence to a pressure movable thermostatic element 50 that operates the pilot valve of the servo-motor-51- controlling the threeway-valve, 42. The above means however, controls only the temperature of the superheating gases in the pipe, 20, so as to maintain this temperature at a fixed point. With a fixed temperature of the superheating gases in the pipe, 20, it is necessary in order to meet and compensate for varying temperature and rate of flow of the oil-vapour, to provide some means by which the quantity of the superheuting gases admitted to the casing, 21, can be varied in conformity therewith, increase being met with increase, and decrease with decrease, in order to keep the temperature of the mixture constant, otherwise the temperature of cracking will vary and an irregular product result.

This condition is met by locating a thermostatic heating chamber, 58, around the vapour pipe, 14, where it emerges or issues from the base of the venturi. The heat of the vapours passing through this pipe generates gaseous pressure in the thermostatic chamber which pressure is transmitted by the small pipe, 55), first to the temperature indicator (i0 'and thence to a pressure movable thermostatic element 50 controlling the servo-motor, 61, operating the throttle valve. 45, in conformity with the temperature variavarying the quantity or rate of flow; and the; tions which valve of course controls the flow *other means is, by keeping the quantity or of the superheating gases.

llll

The digester has already been described, the only remarks to be added are that it is provided with a removable gate, 62, sothat the filling material can be removed at any time. Further an automatic sludge-valve, (i3, is provided which keeps the liquid. level at, 63(53, as shown.

From the digestor 15 the treated products pass to pipe 64 into a condenser 65, the latter being adapted to discharge either into the storage tank 36 or into the recirculating gas line 37 via pipe 66. I

The liquids, after passing throu h the condenser, are then submitted to urther simple distillation treatment. Obviously the distillate may be further purified to any extent desired in the well-known manner.

For cleaning out the small pipes and inaccessible parts of the apparatus, dependence is placed upon blowing out with steam, and should adherent carbon deposits form, these deposits are easily and readily burnt out by means of a stream of high temperature (700 deg. cent.) mixture of air and of carbon dioxide (CO from a suitable gas producer. This mixture will quickly clear out the carbon, as the combustion is very rapid, evolving volumes of sparks, the cessation of which indicates that the surface is clean. There is no danger of destruction of the metal, as the mixture is turned off the moment the sparks cease, and at the same time the temperature quickly drops owing to cessation of combustion.

Referring again to Figure 1, the method of operating the apparatus is as follows 'lhe pressure-regulator, 89, having been set to keep the system under some selected pres.- sure of operation, a pressure-head is gradually built up in the Venturi-tube by spraying oil into the heated converging Venturi mouthpiece or chamber, wherein the fine oil-mist or spray is instantly vapourized, or if hydrocarbon is being used, that produces an unvapoi'lrizable residue, the lighter portion of the oil is at once flashed into vapour, whilst the heavy unvapourizable portion flows down the sloping sides of the Venturichambcr to the Venturi-throat, through which it is blown in the form of spray directly into the base or sludge-box, 11.

Until the pressure developed by the oilvapours exceeds that for which the pressure-controller, 39, is set to release the gases and vapours, no flow will take place through the Venturi-throat or through the system, as soon as this point is passed a flow of vapour to thecondenser, 65, will commence, and the pressure registered bythe gauge, 46. will commence to decrease. As long as this decrease continues to take place. the pressure-head is to be still .further built up by increasing the oil-supply to the venturi,

but. as soon as no further fall in pressure.

occurs with increasingoil-feed it isto be understood that the optimum condition of working is reached for that particular set of conditions, and that these conditions are to be adhered to, in order to obtain the best results in production.

The fact must not be lost sight of, that the apparatus illustrated herein is nothing more than a thermodynamic machine of the nature of an injector and is-subject to the same laws. Thus, it is the expansive force of the contained vapours that furnishes the power necessary for operation, and it to lows that, it is immaterial what the nature of these vapours are, or, how they are generated provided the required conditions are met. Thus, oil-vapour froma separate still may be used for operation, or steam ma be substituted for the gases to furnish the cat and pressure necessary to crack the oil in this apparatus.

Under the influence of the pressure developed in the upper chamber of the venturi the velocity of flow of the vapours in this section is gradually but rapidly accelerate/d as the diameter of the section decreases, until the Venturi-throat is reached. Here the velocity attains its highest maximum, and the pressure coincident-1y its lowest minimum, and here the superheated gases used for cracking the oil-vapours and checking undesired gas production, are introduced. This region of course forms the zone of dissociation for the hydrocarbons to be cracked and here according to the principles already laid down the pressure should be lowest and the temperature highest as is the case a shown above.

As the pressure in the Venturi-throat is much lower than that at which the gases are delivered into the casing, 21, these gases find no difliculty in entering the throat-piece and mixing with the oil-vapours therein.

Under the combined influence of low pressure and high temperature the immediatecracking or breaking down of the hydrocarbons mixing with the superheated gases takes place, after which the resulting mixture of gases, vapours, and decomposition products, is immediately projected into the diverging portion oft-he venturi, where slowing of the velocity with progressive recovery of the original pressure takes place, minus a certain small quantity required to maintain the continuity of flow. Under the influence of the restored pres-' sure, recombination, polymerization and hydrogenation rapidly occurs in the cracked products, which are then passed to the condenser for reduction to liquid form Whilst still under pressure.

As a hypothetical illustration of some of the conditions afl'ecting the operations mentioned herein, let us suppose we have a case wherein our Venturi tube is, as in the illustration, 12 inches in diameter in its widest of the venturi.

section, with a 3 inch throat-piece, and in-v vapour flow through the venturi. Here the total pressure required will be 135 pounds plus 25 pounds giving 160 pounds as the pressure required. Now as the diameter of the upper and lower Venturi sections at their widest partis' 12 inches the area of each is 113.0976 square inches. he throatpiece being 3 inches in diameter ias an area of 7.0686 square inches. Thus the throat area is -;;;th of that of either the top or bottom sections of the venturi. Under these conditions the velocity of the vapours in the throat-piece may be expected'to be 16 times greater than at the widest sect ons of the venturi, whilst the pressure Will be th of that existing in the widest part of the inlet inlet pressure, the throat pressure must necessarily be thof this or 10 pounds per square inch. The outlet pressure of the system under which condensation occurs will of course be 160 pounds less the 25 pounds required to maintain the vapour flow, leaving 135 pounds as the exit and operative pressure.

The superheated gases evolved by the process and introduced into the Venturithroat for cracking the oil-vapours will necessarily have this pressure of 135 pounds per square inch where they are introduced into the casing, 21, and it will be easily seen how this high excess of pressure over that existing in the Ventur1-throat must assist the flow of vapours through this part into the high pressure part of the a paratus. .The above remarks are merely ilustrative and are to be so understood, and not to be taken as accurate estimates of operation.

It is believed by the use of a process such as outlined above there will be attained (1) A higher yield of light hydrocarbons, and the product will be of superior quality to that ordinarily manufactured. J

(2) That it will be found that, on the heavy portion of the petroleum there is selective action with freedom from further cracking of the portions in the vapourphase.

(3) There is automatic removal of the' light hydrocarbons-from the sphere of re vaction as fast as formed.

4) There is high economy of heat.

5) There iseasy and complete removal of all ca'rbon formed.

(6) There is high oil-converting capacity with small dimensions of plant.

(7) There is perfect control of tempera- Thus as 160 pounds is the ture and pressure as each constitutes a sepa rate and independent variable, Where oilvapour only is cracked.

18) There is absolute safety of operation un er all conditions because in the heated zone the vapourizable liquid is practically all expanded into the vapour form and is incapable of developing sudden and excessive pressures.

Having thus described my invention, what I claim and desire to secure by Letters Patent of the United States is z- 1. The process of pyrogenetically cracking hydrocarbons which consists in utilizing the inter-convertibility of potential into kinetic and kinetic into potential energy for efi'ecting, as required, variations in pressure, of the vapors undergoing treatment while supplying suiiicient heat to such vapors to efi'ect the pyrogenetic cracking of the hydrocarbon contained therein.

2. The process of pyrogenetically cracking hydrocarbons which consists in developing oil-vapor under pressure, reducing the pressure of said vapors by converting the pressure into velocity, supplying suflicient additional heat to the vapors while in this state of reduced pressure, to effect their dissociation, progressively removing from the heated zone, the dissociated vapors along with particles of tar and coke produced therein, then restoring the pressure of the vapors by reconverting their velocity into pressure and finally condensing the products so formed.

3. For the purpose of cracking hydrocarbons, an oil still consisting of a Venturi tube the cross-section of which first diminishes to a minimum and then sharply increases to a maximum and which by its shape is adapted 105 for utilizing the interconvertibility of pressure and velocity energy for securing a re duction of the pressure of oil vapors developed therein, as a preliminary to superheating said vapors under reduced pressure, the 110 still by reason of its shape and dimensions further serving to restore the pressure of said vapors by converting their velocity into pressure.

4. In an apparatus of the class described, 116 the combination comprising a Venturi tube,

means for heating the inlet chamber thereof,

ing high boiling point hydrocarbons, subjecting said vapors to heat to develop a rela- 6. The continuous process of producing hydrocarbon oils having low boiling pointsfrom hydrocarbon oils aving high boiling points, which consists in vaporizing the original material to be treated, subjecting said vaporized material to a variable pressure treatment while maintaining a uniform temperature at an optimum value in the zone of.

treatment, utilizing the reciprocal conversion of pressure intovelocity for reducing the pressure of the vaporized material and contacting it while under this reduced'pressure with superheated gases previously evolved by the like step of the process itself, and then restoring the pressure by reducing the velocity of said vapors. v I

7. The process which consists in heating high boiling point hydrocarbons to a relatively high temperature, then introducing the said material through a conduit into a chamber of relatively large cross-sectional area with respectto said conduit, then subjecting said material to a relatively high antogenously developed pressure while maintaining the temperature 'belowthat at which substantial cracking would occur, then passing the vaporized material at an increased rate of flow through a second chamber of considerably smaller average cross-sectional area than the average cross-sectional area of the first chamber and subjecting the material by contact with hot fixed gases in said second chamber to a cracking temperature suflicient to materially crack the said materials treated, then again increasing the pres-' sure upon said materials and condensing the condensable portions thereof while still subjecting said materials to high pressure.

8. In an apparatus of the class described, the combination. comprising a Venturi tube 1 I having an inlet chamber converging to a central elongated throat of substantially uniform cross-sectional area throughout a greater portion of the length-thereof, means for continuously supplying heated fluid to the inlet chamber, means for supplyin a different heated fluid through the wal of said 6 throat to the first fluid, and a condenser in communication with the outlet of said Venturi tube.

9. In an apparatus of the class described, the combination comprising a Venturi tube, means for heating the inlet chamber thereof and means for automatically controlling the temperature of saidinletchamber to correct variations from a selected ,7 predetermined optimum temperature, said means including a gaseous pressure thermostat located within and subject to the heat of the inlet chamber of the venturi; fuel supply and temperature control valves, and a'motor governed by said thermostat for controlling one of said valves.

10. In an apparatus of,the class described, the combination comprising a Venturi tube having an inlet chamber converging to a central elongated throat of substantially uniform cross-sectionalarea thro'u hout a greater portion of the length thereof a tubur jacket surrounding this throat piece, means for continuously supplying heated fluid to the jacket, means for heating the fluid and means for automaticall controlling the temperature of said fluid y mixing therewith more or less cool fluid of a similar nature, said means comprising a gaseous pressure thermostat aflected by the heat of sad fluid supplied to said jacket, a temperature control valve, and a motor governed by said thermostat for controlling said valve.

' 11. In an apparatus of the class described, the combination comprising a Venturi tube having an inlet chamber converging to a central elongated throat of substantially uniform cross-sectional area throughout a greater portion of the length thereof, a tubular jacket surrounding thi throat piece, means for continuously supplying heated fluid to-the jacket, means for malntaining the temperature of this fluid uniform and means for automatically varying the quantity of heated fluid supplied to the jacket to compensate for variations of oil-vapor flow in the venturi, said means comprising a gaseous pressure thermostat, subject to the heat of the hydrocarbon vapors issuing from the outlet of the venturi, a valve for controlling the quantity and rate of flow of the heating fluid supplied to the jacket, and

a motor governed by said thermostat for controlling said valve.

12. In an apparatus of the class described,

a Venturi tube having a closed conicallyshaped vaporizing chamber or mouthpiece with its central axis substantially vertically arranged and having inclined walls converging to the Venturi throat, a means for delivery of a liquid intothe chamber, means arranged to spread the liquid over the walls of such chamber, and means for heatingthe sion and arranged so as to spread a liquid in a thin film over the inner wall of the chamber, a vapor takeoff connecting with the lower end of the Venturi tube, means for maintainin" a layer of liquid of uniform depth 7 in the lower. ortion of such tube formin a llqllld sea therein, and means of said tube, means whereby the lower portion of saidtube is extended out of and below the heating zone of said furnace, means arranged within the upper part of the tube and located above the" heated zone for continuously supplying a liquid to the tube, means arranged to direct the liquid against the inclined walls of the tube, and means arranged to insure control of liquid flow, said last mentioned means comprising a constant flow valve located in the oil-line leading to the tube, a vapor take-off connecting with the lower extension of the Venturi tube DONALD 'LEE THOMAS. 

